A major cause of damage to road surfaces is the entrapment or retention of water beneath the road surface, in the road base or sub-base. Such retained water can cause potholes, buckles and gaps in the pavement, as well as cracking or crumbling of the pavement, and can lead to premature collapse or failure of the roadbed. Rapid subsurface drainage of the roadbed is thus critical to extending the useful life of the highway.
The HYDRAWAY™ drain (a trade mark of Midwest Diversified Technologies, Inc.) is a known drainage system useful for this purpose. It comprises a tubular, internally supported geotextile fabric filter disposed in the ground beneath or preferably adjacent to a covered ground surface, for example, in the sub-base of a highway or pavement. The filter support is constructed of a somewhat rigid but resiliently deformable polyethylene core, about which the filter is circumferentially disposed, and to which the filter is bonded. This system is disclosed in U.S. Pat. Nos. 4,793,728 and 4,898,494. A disadvantage of the disclosed tubular filter is the polyethylene core, which provides inadequate support, and has poor compressive strength. The '494 patent discloses that the compressive strength of the core is about 5000 psf. This poor strength makes the tubular filter susceptible to collapse when buried, and susceptible to damage when transported and handled.